In general, a long-neck flange is used to closely connect two pipes to each other, and there is an increasing need for the long-neck flange.
The long-neck flange is also called a lap joint flange or a stub end, and the structure and manufacturing method thereof are various.
As shown in FIG. 1, in a method of manufacturing a long-neck flange according to the related art, a long-neck flange includes a pipe part 1; and a flange part 2 coupled to an end of the pipe part 1, and is manufactured by forming the flange part 2 through the formation of a flat plate in a ring shape and then coupling the formed flange part 2 to the pipe part 1 through welding.
However, in the method of manufacturing a long-neck flange, since it is necessary to perform a process of coupling the flange part 2 to the pipe part 1 as well as a process of forming the flange part 2 with a predetermined size and shape, there are problems in that a manufacturing process is complicated and manufacturing costs are high. Since the pipe part 1 and the flange part 2 are weld using weld beads 4a and 4b, it is difficult to stably maintain the coupling state thereof for a long term, the strength thereof is weak due to thermal stress locally generated in the welded part, and the welded part is inconveniently processed again in a desired shape after the welding is performed.